This invention relates to clay pigeons.
In the sport of clay pigeon shooting targets (known as xe2x80x9cclay pigeonsxe2x80x9d or xe2x80x9cclaysxe2x80x9d) are flung into the air by a launching device (known as a xe2x80x9ctrapxe2x80x9d) and a participant in the sport attempts to shoot the moving target using a shotgun. On impact of shot, the target is intended to break up.
Clay pigeons are conventionally manufactured using a hot moulding process in which milled limestone and hot pitch are moulded together, the pitch comprising approximately 20 -40% by weight. Handling hot pitch has health and safety implications for workers making the clay pigeons.
One problem with competitive clay pigeon shooting is that sometimes an impact from a single shot will not be sufficient to cause the target to break up fully and this can lead to dispute over whether a clay pigeon has been hit or not. Ideally a clay pigeon should disintegrate even if hit by just one shot. This ideal is not normally met. At the same time the clay pigeon should be strong enough not to disintegrate in transport or when flung from the trap.
A further problem is the quantity of material that is left after a major clay pigeon shooting event. Every clay pigeon that goes up comes down to ground somewhere, either intact or in pieces. Approximately 350 million clay pigeons are sold per annum in the United Kingdom alone, and this represents a lot of material strewn on the ground (equivalent to approximately 3,500 tonnes per annum). The fact that the clay pigeons, if not hit or if only glancingly hit, leave large sized debris means that the material of the clay pigeons resists degradation for some time. The pitch present in the clay pigeons further impedes degradation.
Additionally, pitch tars have been classified as potential or actual carcinogens in some jurisdictions and there is a risk of contaminating ground waters with run off where there is a large quantity of clay pigeon debris, for example at shooting grounds.
U.S. Pat. No. 5649807 disclosed the manufacture of clay pigeons comprising at least 50% by weight clay, and 5 -50% calcium containing additive (which could be limestone powder) which reduces the drying shrinkage of the (wet) clay. A plasticity-improving component such as a lignosulphonate could also be used. Clay pigeons are made from this mixture by pressing the mixture in a mould and removing them while still in a plastic (wet) state. Because the moulded clay pigeon is still wet careful handling to remove the clay pigeon from the mould is required. Even so such a process will cause problems in the reproducibility of the shape, dimensions, weight, and texture of the clay pigeons produced, with a consequent variability in their flying characteristics. This is not desirable.
The present invention aims to overcome the problem of handling plastic (wet) clay pigeons by forming the clay pigeons by compaction from a dry powder.
FR-A-2575818 discloses a clay pigeon formed by drying pressing from a clay, and incorporating a stabiliser (rapid setting cement or lignosulphite). The function of the lignosulphite is to provide mechanical stability to the pressed pigeon.
The applicants have found that clay pigeons produced with clay and such a binder are too fragile.
The present invention aims to overcome the problem of fragility of clay pigeons by providing an improved binding system.
GB-A-2337003 discloses a clay pigeon comprising sulphur, a filler, and a sulphur modifier which may be a lignin sulphonate. The lignin sulphonate modifies the behaviour of the sulphur. Such clay pigeons are expensive to form however, requiring the melting of the sulphur, dwelling at temperature, and subsequent casting.
The present invention aims to overcome the problem of high cost forming routes by using dry pressing powders.
Accordingly the present invention provides a method of making clay pigeons by the step of compacting a dry powder comprising an inorganic filler and a binder, the inorganic filler comprising greater than 50% by weight calcium carbonate.
The inorganic filler may comprise more than 60%, 70%, or 80% by weight calcium carbonate if desired.
In the context of this application the term xe2x80x9cdryxe2x80x9d need not mean totally free of water but does mean comprising less than 10% by weight of water based on the amount of the inorganic powder.
The inorganic filler may comprise clay.
The binder may comprise a lignosulphonate compound.
Lignosulphonates are materials obtainable from wood and are available from both hard and soft woods. Lignosulphonates may be modified and include altered cations. For the present invention all lignosulphonates may be used, modified or unmodified, and may include any suitable cation or cations, for example calcium, magnesium, ammonium and sodium.
The clay pigeon may be made by a process in which the inorganic filler and binder are mixed as a slip and spray dried to form the dry powder.
Accordingly the present invention provides a method of making clay pigeons by the step of compacting a dry powder comprising an inorganic filler and a binder, the inorganic filler comprising greater than 50% by weight calcium carbonate.
The inorganic filler may comprise more than 60%, 70%, or 80% by weight calcium carbonate if desired.
In the context of this application the term xe2x80x9cdryxe2x80x9d need not mean totally free of water but does mean comprising less than 10% by weight of water based on the amount of the inorganic powder.
The inorganic filler may comprise clay.
The binder may comprise a lignosulphonate compound.
Lignosulphonates are materials obtainable from wood and are available from both hard and soft woods. Lignosulphonates may be modified and include altered cations. For the present invention all lignosulphonates may be used, modified or unmodified, and may include any suitable cation or cations, for example calcium, magnesium, ammonium and sodium.
The clay pigeon may be made by a process in which the inorganic filler and binder are mixed as a slip and spray dried to form the dry powder.